Effect of liquid scintillating cocktail volume on 3H and 14C measurement parameters using a Quantulus spectrometer

Results of study on the influence of cocktail volume on such measuring parameters as counting efficiency, standard quench parameter (SQP) and figure of merit (FOM) are described. Nine commercial cocktails were tested using a Quantulus spectrometer. Two kinds of vials (low-diffusion teflon-coated polyethylene (LD-PE) and high-performance glass (HP-G)) and two standard solutions (14C and 3H) were used. Measurements were performed at seven quench levels ensured by carbon tetrachloride addition to the scintillation vials. Various quench sensitivity of the studied cocktails was found. Cocktails based on simple benzene-derived solvents revealed the best quench resistance. In general, increasing cocktail volume caused an increase in the counting efficiency. However, the background increased as well, what resulted in FOM diminishing. Studied cocktails revealed also various responses to volume changes.